Chemistry 120-00____
Experiment 7
Name:__________________ Partner_______________________
Date of Expt.: __________________
Instructor’s initials: _____________
Determination of the Total Hardness of H2O Using EDTA
Note: All burette readings accurate to two decimal places.
Part I: Standardization of EDTA
Mass of CaCO3 used =
g
Burette Reading (mL)
VEDTA
Correction
Corrected
(mL)
from Part III
VEDTA (mL)
Initial
final
1
minus
________ mL*
2
from Part III
3
Note: mass of CaCO3 ─ MM → mol of CaCO3 ─ x 1/10 dilution factor →
mol of CaCO3 after dilution ─ 1:1 → mol of EDTA ─  avg. corrected VEDTA → MEDTA
Part II: Analysis of Hard H2O Sample # ___________ Partner’s Sample # ______________
(Use entire content, analytical transfer, rinse sample tube & add rinsing to flask also!)
Burette Reading (mL)
VEDTA
Correction
Corrected
(mL)
from Part III
VEDTA (mL)
Initial
final
1
minus
________
mL*
2
from Part III
3
Note: Avg. corrected VEDTA ─ x MEDTA from Part I → mol of EDTA ─ 1:1 →
mol of Ca2+ ─  0.02500 L x MM of Ca2+ → g Ca2+/ L ─ x 103 mg/g → ppm Ca2+
Part III: Correction for Indicator Blanks
Burette Reading (mL)
VEDTA
(mL)
Initial
final
1
2
Average VEDTA value for
Correction = ________ mL*
3
Lab Write Up:
1. Title: Lab 7 Calibration of and EDTA solution and analysis of a hard water sample
2. Procedure: Explain the preparation of your calcium standard and its use to calibrate
your EDTA solution. Explain what an indicator blank is and why you have to titrate
and calculate this.
3.a. Calculate the concentration of your calcium carbonate standard show your
calculations and report your result.
3.b. Calculate the strength of your EDTA solution and report it.
3.c Report the value of your indicator blank.
3.d. Calculate the concentration of your hard water sample in ppm and report the total
mg of Ca+2 in your hard water sample and report as: Sample #666 had ______ ppm Ca+2
and ______ mg of Calcium.
4. For 5 % extra credit, analyse Victoria Tap water and report the total hardness using
your titration and indicator blank for the calculations. Report the concentration in
ppm. Hint it should be low so it is easy to overshoot this.